1. Field of the Invention
The present invention relates to a method and an apparatus for observing, analyzing, and inspecting a crystal defect, which are suitable for use in the analysis and inspection of a crystal defect, a junction breakage caused by an electrical stress, or the like, inside a wafer in which semiconductor device chips, in particular, compound-semiconductor laser diode device chips are integrated.
2. Related Background Art
A typical compound-semiconductor laser diode device mainly includes laser diode chips in which a stacked structure made of several kinds of semiconductors is formed. An oscillator (stripe) is provided in the laser diode chip. The oscillator confines laser light and amplifies the laser light by resonance. Many technologies have been developed for failure analysis and inspection of the compound-semiconductor laser diode (hereinafter, referred to as a laser diode).
The inspection of the laser diode includes an electrical and optical characteristics measurement. A near field pattern (NFP) observation method is well known as the electrical and optical characteristics measurement. In the NFP observation method, a light-emission stage in a laser-light emission position at an end face of the laser diode chip is two-dimensionally found with an infrared camera to observe a light-emission shape of the laser diode, and an abnormality is discriminated by comparing the laser diode of the inspection subject to the nondefective unit. The observation of the NFP observation method is performed in a manner that magnifies the light-emission position with an optical microscope while the laser diode chip is caused to emit the laser light, finds the NFP of the light-emission position with the infrared camera, and displays the NFP on a monitor screen (for example, see “Insight into Semiconductor Laser” 2nd edition, edited by Minoru KONUMA and Mitsuyoshi SHIBATA, Kougakutosho Ltd., May 25, 1998)).
An aging method for screening a defective unit due to the crystal defect is also the well-known art. In the aging method, the defective unit is discriminated from a change in an optical output after a predetermined time has elapsed.
In the conventional method and apparatus for analyzing and inspecting a semiconductor laser diode device described above, there are the following problems.
In the method for measuring electrical and optical characteristics, although the defective unit, which does not satisfy initially-required design specifications, can be detected, the defective unit which is degraded with time by the crystal defect located inside the chip cannot be detected. In the NFP observation method, because only the end face reflecting the laser light is observed, only a trace of catastrophic optical damage (COD), which appears as optical information on the end face can be detected, and it is difficult to check an abnormality such as a crystal defect located inside the chip.
In the aging method, it is necessary to perform operations for all the finished units in a high temperature environment and it is also necessary to pay close attention to handling of the device or the apparatus so that the breakage of the device is not generated during the aging. Further, sometimes it takes several hours to tens of hours to perform the aging. Therefore, from a viewpoint of manufacturing cost, the aging method has a large problem. Particularly, the requirement of the aging for long hours becomes a large obstacle in mass production and reduction of the manufacturing cost cannot be expected.
Further, in these conventional inspection methods, basically, it is necessary to perform the inspection in the state in which each chip is cut out from the wafer or in the state in which the device is almost finished. Therefore, it requires time to be spent to perform the inspection in the case of total inspection, and it is impossible to completely detect the defective unit in the case of a sampling inspection. When the defective unit is detected, there is also the problem that the processes through which the defective unit is produced go to waste.